2016 Water Quality Summary Report

UVALDE TETRACHLOROETHENE PLUME

I n 1979, a fire at an industrial dry-cleaning operation on the east side of Uvalde, Texas, resulted in a release of tetrachloroethene (PCE) into the aquifer and the subsequent creation of a groundwater plume that

extends approximately two miles down gradient to the east. The PCE was first detected in a City of Uvalde water supply well (Edwards Aquifer well) in 1982, which was removed from service. Groundwater

monitoring is continuing in the area, particularly at sample location YP-69-51-114. This location has been sampled quarterly since August 2014 and routinely indicates low level detections of PCE.

BACTERIA SAMPLES AND PRIVATE WELL OWNERS In 2016, the EAA collected 39 bacteria samples from 34 wells (30 Edwards wells and four Trinity wells). Only three samples tested positive for bacteria, Escherichia coli (E. coli). The EAA collects

bacteria samples from wells before any chlorination to assess the presence or absence of bacteria in rawwater samples fromthe aquifer. These sample results are not directly comparable to bacterial samples

collected by most public water supply systems, which are generally collected after chlorination. Samples ranged in concentration from non-detectable to three most probable number (MPN) per 100 milliliters of water. E. coli bacteria analyses are used to indicate the possible presence of fecal matter in groundwater and surface water.